Memory Device Differential Voltage State Detection
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Solution Overview
Problem
Conventional nitride storage non-volatile memory (NVM) devices experience erroneous operations due to increased drain operation voltage or completion of program/erase cycles, leading to a retraction of the operating boundary and increased vulnerability to errors.
Innovation Solution
A memory device with a comparator and switching circuits that apply different operating voltages to generate working currents, which are then transformed into voltages to calculate a partial differential value, allowing for accurate determination of the program/erase state, thereby maintaining a fixed operating boundary across varying voltages and cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the drain operation voltage is increased, then the operating speed is improved, but the operating boundary retracts and erroneous actions occur
Solution Approach 1:
The patent changes the parameter used for state determination from absolute voltage threshold to differential voltage (difference between first and second operating voltages). This parameter transformation allows the system to maintain reliable state detection even when absolute voltage levels shift due to DIBL effect or aging, thereby resolving the contradiction between operating speed and reliability
Solution Approach 2:
The patent implements a feedback mechanism by comparing the differential voltage against a reference voltage to determine program/erase states. This feedback approach compensates for voltage fluctuations and boundary retraction, maintaining reliable operation at higher drain voltages without causing erroneous actions
2Productivity
If the memory device performs program/erase cycles, then the data storage function is achieved, but the operating boundary retracts and vulnerability to errors increases
Solution Approach 1:
The patent transforms the state detection parameter from absolute voltage to differential voltage, which remains stable throughout program/erase cycles. This parameter transformation eliminates the operating boundary retraction problem that occurs after cycles, maintaining reliability while preserving full program/erase functionality
Solution Approach 2:
The patent applies preliminary compensation by using differential voltage measurement that inherently compensates for threshold voltage shifts caused by program/erase cycles. This preliminary action prevents operating boundary retraction before it can affect subsequent operations, ensuring consistent reliability
3Device complexity
If the conventional voltage threshold method is used, then the device structure is simple, but the operating boundary retracts leading to erroneous actions
Solution Approach 1:
The patent changes the detection parameter from absolute voltage to differential voltage, which provides stability against operating boundary retraction. This parameter transformation achieves reliable operation without significantly increasing device complexity, as it can be implemented using existing voltage sources and comparison circuitry
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents erroneous actions by maintaining a stable operating boundary, enabling reliable operation across multiple program/erase cycles and varying drain operation voltages, ensuring accurate state determination.
Implementation Method 1
Through hot electron or hot hole injection, the memory cell can be erased or programmed
Implementation Method 2
The first passive device and the second passive device may be capacitors or resistors
Implementation Method 3
The difference between the second working voltage and the first working voltage is divided by the difference between the second operating voltage and the first operating voltage to obtain a partial differential value
Implementation Method 4
the operating voltage difference OM2 between the curves 101 and 103 is reduced to about 0.46V (1.66V−1.2V) due to the drain inductance barrier lowering (DIBL) effect
Data Source
AI summary
A method of operating a memory device adapted for determining a program/erase state of a memory cell in the memory device. The method includes applying a drain operation voltage to a drain of the memory cell so that the memory cell generates a working voltage. The working voltage is a function of the drain operation voltage. Then, the working voltage to the drain operation voltage is differentiated to obtain a slope of the working voltage to the drain operation voltage. The program/erase state of the memory cell is determined according to the slope.